Tunable resonant structure



April 12, 1955 R. J. JACOB! TUNABLE RESONANT STRUCTURE 2 Sheets-Sheet 1 Filed Nov. 27 1951 INVENTOR. RICHARD J. JACOB! BY g E ATTORNEY April 12, 1955 R. J. JACOB! TUNABLE RESONANT STRUCTURE 2 Sheets-Sheet 2 Filed Nov. 27, 1951 DDDDDDDDiG Own-Dummwn an INVENTOR. RICHARD J. JACOBI BY t g ATTORNEY United States Patent TUNABLE RESONAN T STRUCTURE Richard J. Jacobi, Oak Park, Ill., assignor to Raytheon ManufacturingCompany, a corporation of Delaware Application November 27, 1951, Serial No. 258,445

6 Claims. (Cl. 333-82) The present invention relates in general to resonant tuning systems, and more particularly to a tunable resonant structure adaptable for use in a distributed constant radio frequency tunable resonant circuit.

In tunable resonant structures, having a wide range to cover in the ultra-high frequency band, movable shorting bars have been used for selecting the resonant frequency by controlling the electrical characteristic length of the conductors. However, such shorting bars provided an open line section behind the resonant section. Therefore, an open section is provided with the shorting bar somewhere in the electrical center. Such a condition hinders the operation of an oscillator when both open sections have approximately the same resonant frequency, by dissipating the energy therein in both sections, thereby cutting ofi the oscillatory state. Further, the shorting bars heretofore used have never been adaptable for accurate micromatic tuning.

Accordingly, an important object of the present invention is to provide a tunable resonant structure adaptable for use in a distributed constant tunable resonant circuit wherein there is no open section behind the resonant portion thereof by providing a ribbon shorting member.

Another object of the present invention is to provide a tunable resonant structure adaptable for use in a distributed constant tunable resonant circuit wherein accurate tuning is provided by having a variably positioned shorting member driven by a gear mechanism.

Another object of the present invention is to provide a tunable resonant structure adaptable for use in a distributed constant tunable resonant circuit wherein accurate tuning is provided by having a variably positioned shorting member sprocket driven.

Another object of the present invention is to provide a tunable resonant structure adaptable for use in a distributed constant tunable resonant circuit wherein improved oscillatory characteristics and accurate tuning are provided by having a ribbon shorting member sprocket driven.

Another object of the present invention is to provide a tunable resonant structure adaptable for use in a distributed constant tunable resonant circuit wherein improved oscillatory characteristics and accurate tuning are provided by having a ribbon shorting member driven by a gear mechanism.

Another object of the present invention is to provide a tunable resonant structure adaptable for use in a distributed constant tunable resonant circuit that occupies a minimum of space by providing therein an arcuate shaped conductor and a contour conforming flexible ribbon shorting member.

Another object of the present invention is to provide a durable tunable resonant structure adaptable for use in a distributed constant tunable resonant circuit by providing a U-shaped channel conductor for receiving the ribbon shorting member.

Other objects will appear upon further perusal of the detailed description taken in conjunction with the accompanying drawings in which:

Figure l is a partial schematic diagram illustrating an oscillatory circuit utilizing the tunable resonant structu'r'e embodying the present invention;

Figure 2 is a front elevational view illustrating the novel tunable resonant structure embodying the present invention;

Figure 3 is a plan view of the tunable resonant structure;

Figure 4 is a sectional view taken substantially along the line D, D, of Figure 2 and particularly illustrating the tooth edge of the ribbon shorting member and the sprocket gear wheel.

Figure 4A is a partial rear view particularly illustrating the guide members for the flexible ribbon shorting member of the tunable resonant structure;

Figure 5 is an enlarged sectional view taken substantially along the line B, B, of Figure 3 and particularly illustrating the structure of the U-shaped channel conductor;

Figure 6 is an enlarged sectional view taken substantially along the line C, C, of Figure 3 and particularly illustrating the shorting contact structure of the ribbon shorting member;

Figure 7 is a front elevational view of a modification of the tunable resonant structure embodying the present invention;

Figure 8 is a top view of the modification of the tunable resonant structure;

Figure 9 is a sectional view taken substantially along the line E, E, of Figure 7 and particularly illustrating the structure of the U-shaped channel conductor;

Figure 10 is an enlarged sectional view taken substantially along the line F, F, of Figure 8 and particularly illustrating the sprocket driving mechanism and the ribbon shorting member; and

Figure 11 is a partial schematic diagram illustrating an oscillatory circuit utilizing a modification of the novel tunable resonant structure embodying the present invention.

Briefly described, a tunable resonant structure is herein provided adaptable for use in a distributed constant tunable resonant circuit. The tunable resonant structure functions on a transmission line theory and is basically a quarter wave length section.

In one embodiment, the tunable resonant structure comprises a U-shaped channel conductor made of suitable conducting material, such as brass. For controlling the electrical characteristic length of the U-shaped channel conductor, a flexible ribbon shorting member or tape made of suitable conducting material, such as Phosphor bronze, is provided. The flexible ribbon shorting member is suitably received by the U-shaped channel and cooperatively engages the conductor for establishing the electrical characteristic length thereof.

For variably positioning the flexible ribbon shorting member relative to the conductor, one embodiment of the present invention provides a suitable gear driving mechanism which intermeshes with the tooth edge of the flexible ribbon shorting member for imparting lateral movement thereto relative to the U-shaped channel conductor. Another embodiment of the present invention provides a suitable sprocket driving mechanism which is suitably received by the apertures in the flexible ribbon shorting member for imparting lateral movement thereto relative to the conductor.

In more detail, tunable resonant structures are herein provided to cover the UHF television band. Lump circuit perameters are both impractical and impossible to use to cover the range between 470 megacycles and 900 megacycles.

Referring now to Figures 1-6, inclusive, one embodiment of the novel tunable resonant structure comprises a U-shaped channel conductor 11 made of suitable conducting material, such as three separate conducting strips 11a, 11b and 110, as shown in Figure 5. It is to be noted that the U-shaped conductor 11 may be integrally formed from a single piece, as shown in Figure 9. For securing the strips 11a, 11b and 110, suitable means are provided, such as rivets 12. Each conductor strip, such as 11a and 11c, is a stamping, having spaced-apart portions 11d and lle.

For controlling the electrical characteristic length of the U-shaped channel conductor 11, thereby selecting the resonant frequency of the tunable resonant structure, a flexible ribbon shorting member 13, or tape, is provided, made of suitable conducting material, such as Phosphor bronze. The shorting member 13 is an elongated flexible ribbon having teeth 14 at one edge thereof. The conductor 11 has the strips 11a and 110 suitably spaced by the strip 11b so as to receive the flexible ribbon shorting member 13 to provide lateral movement therebetween and still cooperatively engage the flexible ribbon shorting member 13 for establishing electrical contact engagement.

For providing improved contact engagement between the conductor strips 11a and 11c and the shorting member 13, one end of the ribbon shorting member facing the open end of the tunable resonant structure is provided with an outwardly extending flange 130, as shown in Figure 6. In addition thereto, a flexible ribbon strip 14 made of suitable conducting material, such as Phosphor bronze, is secured to the flexible ribbon shorting member 13, as shown in Figure 6, by suitable means, such as solder. The flexible ribbon strip 14 has an outwardly extending flange 14a for further improving the contact engagement between the shorting member 13 and the conductor 11.

It is to be particularly noted that it is a feature of the present invention to prevent two open line sections in the tunable resonant structure by providing a ribbon shorting member that is elongated and extends to the shorted end of the tunable resonant structure. Noteworthy is the advantage gaiued by this feature; in the event two open end line sections are present with a short in the middle thereof, the energy is dissipated in both sections, thereby hindering the oscillatory state and at times preventing continuous oscillations. This is particularly noticeable in the event both sections have approximately equal wave length.

In order to provide a tunable resonant structure that would occupy a minimum of space, another feature of the present invention is to provide an arcuate configuration for the U-shaped conductor 11, which in the preferred embodiment is semi-circular, as shown in Figure 2. The flexible ribbon conductor 13 has a configuration which is also substantially semi-circular and conforms to the contour of conductor 11. it is to be understood that the conductor 11 and the ribbon shorting member 13 can be straight pieces.

For variably positioning the flexible ribbon conductor 13 relative to the U-shaped conductor 11 in order to select the resonant frequency of the tunable resonant structure, a gear driving mechanism 15 is provided.

Suitable means, such as bracket 16, is provided for mounting the gear mechanism 15 to the tunable resonant structure and is secured to the conductor 11 by suitable means, such as a screw and nut arrangement 17.

A rotatable shaft 18 is suitably received by an aperture in the bracket 16. At one end of the shaft 18 is suitably positioned a collar 19 fixedly secured thereto for preventing excessive lateral displacement of the shaft 18. For rotating the shaft 18 suitable means are provided, such as knob 20, made of suitable insulating material, such as hard rubber or plastic. For driving the variably positioned ribbon shorting member 13, a spur gear wheel 21 is provided which is fixedly secured to the shaft 18 and suitably positioned thereon to cooperatively engage the tooth edge 14 of the flexible ribbon shorting member 13. Washer 22 is positioned between the spur gear wheel 21 and the bracket 16, and spring washer 23 is positioned between collar 19 and bracket 16 to further prevent excessive lateral movement of the shaft 18.

For guiding the movement of the flexible ribbon shorting member 13 at the open end of the tunable resonant structure, guide members 24 and 25 are provided. The guide members 24 and 25 are secured to the conductor 11 by suitable means, such as the screw and nut arrangement 17. The guide members 24 and 25 have inturned portions 240 and 25a, respectively, facing one another so as to provide a narrow guiding passageway for the portion of the shorting member 13 protruding out of conductor 11 at the open end of the tunable resonant structure. For retaining the ribbon member 13 so that the tooth edge 14 constantly engages the spur gear wheel 21, retaining member 26 is provided. The retaining member 26 is a right angle piece suitably secured to the bracket 16 at the straight portion 26a by the screw and nut arrangement 17. The bent portion 26b of the retaining member 26 at one edge thereof abuts against the edge of the shorting member 13.

In operation, an operator rotates the knob to rotate the shaft 13 which in turn rotates the spur gear wheel 21 secured thereto. The movement of the spur gear wheel 21 imparts lateral movement to the flexible ribbon shorting member 13 relative to the U-shaped channel conductor 11 by having the spur gear wheel 21 intermesh with the teeth 14 of the shorting member 13.

Referring now to Figure l, for a preferred line tuned oscillatory circuit 28 utilizing the novel structure of the present invention, the oscillatory circuit 28 comprises a suitable triode tube 29 having the plate thereof suitably connected to the spaced portion 1142 of the U-shaped channel conductor 11 at the open end of the tunable resonant structure. The plate of the tube 29 is suitably connected to B+ potential by conductor 11. The grid of the tube 29 is suitably connected to the spaced portion 11a of the conductor 11 through a blocking condenser 33 at the open end of the transmission line.

The operation of the oscillatory circuit 28 is conventional in that a quarter wave length section is variably tuned to select the oscillatory frequency for the line tuned oscillator 28.

Referring now to Figures 8-10, inclusive, another embodiment of the novel tunable resonant structure comprises a U-shaped channel conductor 31 made of suitable conducting material, such as brass. As shown in Figure 9, the U-shaped channel conductor 31 is an integrally formed piece. The U-shaped channel conductor 31 has spaced-apart portions 31a and 31b. The spaced-apart portions 31:: and 3112 have included therein grooves 310, as shown in Figure 9, to provide a channel or passageway for suitably receiving a ribbon shorting member or tape 32. The grooves 31c are suitably spaced so as to enable the ribbon shorting member 32 to have lateral movement therethrough and still enable the "ribbon shorting member 32 to cooperatively engage the U-shaped conductor 31 for establishing electrical contact engagement.

For controlling the electrical characteristic length of the U-shaped channel conductor 31, thereby selecting the resonant frequency of the tunable resonant structure, the flexible ribbon shorting member 32 is provided and is made of suitable conducting material, such as Phosphor bronze. The shorting member 32 is an elongated flexible ribbon having a series of suitably spaced and shaped apertures 320 at the central portion thereof. The flexible shorting ribbon 32 is suitably received by the grooves 320 so as to enable lateral movement therethrough relative to the U-shaped conductor 31 and still cooperatively engage the U-shaped conductor 31 for establishing electrical contact engagement therewith. The flexible ribbon shorting member conforms to the contour of the U-shaped channel conductor 31.

For variably positioning the flexible ribbon shorting member 32 relative to the U-shaped conductor 31 in order to select the resonant frequency of the tunable resonant structure, a sprocket driving mechanism 33 is provided.

Suitable means, such as brackets 34 and 35, are provided for mounting the sprocket driving mechanism 33 to a support means, such as an insulated terminal strip 36 of the tunable resonant structure. The sprocket driving mechanism 33 and the U-shaped conductor 31 are secured to the terminal strip 36 by suitable means, such as a screw and nut arrangement 37.

Rotatable shaft 38 made of suitable insulating material is suitably received by apertures in the brackets 34 and 35. For driving the variably positioned ribbon shorting member 32, a sprocket wheel 39 is provided which is fixedly secured to the shaft 38 and hasprojections 39a thereon which are suitably received by the apertures 32a for cooperative engagement with the flexible ribbon shorting member 32 for imparting lateral movement thereto, relative to the U-shaped conductor 31.

For guiding the movement of the flexible ribbon shorting member 32 protruding out of the portion of the conductor 31, an arcuate guide member 40 is provided and in the preferred embodiment is substantially circular. The guide member 40 is secured to the terminal strip 36 by suitable means, such as a nut and screw arrangement 42. The flexible ribbon shorting member 32 engages the inner surface thereof and Winds in a spiral configuration, as shown in Figure 7.

In operation, an operator rotatesthe shaft 38 which in turn rotates the sprocket wheel 39 secured thereto. The movement of the sprocket wheel 39 imparts lateral movement to the flexible ribbon shorting member 32 relative to the U-shaped channel conductor 31 by having the projections 39a of the sprocket wheel 39 engaging the shorting member 32 by extending through the apertures 32a.

Referring now to Figure 11, for a preferred line tuned oscillatory circuit 43 utilizing the novel tuning structure of the present invention, the oscillatory circuit 43 comprises a suitable triode tube 44 having the plate thereof suitably connected to the spaced portion 31b of the U-shaped channel conductor 31 at the open end of the tunable resonant structure. Through the conductor 31, the plate of the triode tube 44 is connected to B+ potential. ably connected to the spaced portion 31a of the conductor 11 through a blocking condenser 45 at the open end of the transmission line.

The operation of the oscillatory circuit 43 is conventional in that a quarter wave length section is variably tuned to select the oscillatory frequency for the line tuned oscillatory circuit.

It is to be understood that variations and modifications may be eifected without departing from the scope of the appended claims.

I claim:

1. In a tunable resonant structure adaptable for use in a distributed constant tunable resonant circuit, a source of ultra high frequency energy, a distributed constant transmission line comprising two conductors connected to said source of energy, a ribbon shorting member of conductive material conductively engaging both conductors of said transmission line along a length thereof extending from the end of said transmission line remote from the connection of said transmission line to said source for controlling the electrical characteristic length of said transmission line, and means variably controlling the length of said ribbon shorting member engaging said transmission line for varying the length of said transmission line engaged by said shorting member and thus selecting the resonant frequency of said tunable resonant structure.

2. In a tunable resonant structure adaptable for use in a distributed constant tunable resonant circuit, a source of ultra high frequency energy, a distributed constant transmission line comprising two conductors each of which is in the form of a U-shaped channel, said conductors being connected to said source of energy, a ribbon shorting member of conductive material movable in said U-shaped channel conductors and conduc-- tively engaging both of said U-shaped channel conductors along a length thereof extending from the end of said transmission line remote from the connection of said transmission line to said source for controlling the electrical characteristic length of said transmission line, and means variably controlling the length of said ribbon shorting member engaging said U-shaped channel conductors for varying the length of the transmission line engaged by said ribbon shorting member and thus selecting a resonant frequency of said tunable resonant structure.

3. In a tunable resonant structure adaptable for use in a distributed constant tunable resonant circuit, a source of high frequency energy, a distributed constant transmission line comprising two conductors, said transmission line having an arcuate configuration for conserving space and connected to said source of energy,

a flexible ribbon shorting member of conductive material having a contour conforming to the configuration of said transmission line and conductively engaging both conductors of said transmission line along a length thereof extending from the end of said transmission line remote from the connection of said transmission line to said source for controlling the electrical characteristic length of said transmission line, and means variably controlling the length of said ribbon shorting mem- The grid of the triode tube 44 is suit-' ber engaging said transmission line for varying the length of the transmission line engaged by said ribbon shorting member and thus selecting the resonant frequency of said tunable resonant structure.

4. In a tunable resonant structure adaptable for use in a distributed constant tunable resonant circuit, a source of ultra high frequency energy, a distributed constant transmission line comprising two conductors connected to said source of energy, a ribbon shorting member of conductive material conductively engaging both conductors of said transmission line along a. length thereof extending from the end of said transmission line remote from the connection of said transmission line to said source for controlling the electrical characteristic length of said transmission line, and a gear driving mechanism variably controlling the length of said ribbon shorting member engaging said transmission line for varying the length of the transmission line engaged by said ribbon shorting member and thus selecting the resonant frequency of said tunable resonant structure.

5. In a tunable resonant structure adaptable for use in a distributed constant tunable resonant circuit, a source of radio frequency energy, a distributed constant transmission line comprising two conductors connected to said source of energy, a ribbon shorting member of conductive material conductively engaging both conductors of said transmission line along a length thereof extending from the end of said transmission line remote from the connection of said transmission line to said source for controlling the electrical characteristic length of said transmission line, and a sprocket driving mechanism variably controlling the length of said ribbon shorting member engaging said transmission line for varying the length of the transmission line engaged by said ribbon shorting member and thus selecting the resonant frequency of said tunable resonant structure.

6. In a tunable resonant structure adaptable for use in a distributed constant tunable resonant circuit, a source of ultra high frequency energy, a distributed constant transmission line having a support means, said transmission line comprising two channel conductors attached to said support means and connected to said source of energy, a flexible ribbon shorting member of conductive material conductively engaging and variably positioned in both of said channel conductors for controlling the electrical characteristic length of said conductors and having a portion thereof extending out of said conductors from the ends of said conductors remote from the connection thereof to said source of energy, a ribbon guiding member having a circular configuration attached to said support means and having the inner peripheral surface thereof engaged by the portion of said flexible ribbon shorting member extending out of said conductors for guiding said ribbon shorting member, and means variably positioning said flexible ribbon shorting member in said channel conductors, whereby the portion of said flexible ribbon shorting member extending out of said conductors engages the inner peripheral surface of said guiding member for providing a spiral configuration.

References Cited in the file of this patent UNITED STATES PATENTS 2,159,782 Conklin et al. May 23, 1939 2,246,928 Schick June 24, 1941 2,292,254 Van Beuren Aug. 4, 1942 2,405,229 Mueller et al. Aug. 6, 1946 2,468,147 Vonada Apr. 26, 1949 2,516,990 Herold Aug. 1, 1950 2,523,725 Schmidt Sept. 26, 1950 2,581,680 Martenot Jan. 8, 1952 

